A morning sounding, gathered via data from a weather balloon launched at the NWS in Upton, New York showed a developing unstable environment — and sufficient wind shear for organization of strong and severe thunderstorms. An approaching disturbance in the mid and upper levels will aid in the development of strong to severe thunderstorms, which will be fueled by a moderately unstable environment throughout the area. Organized thunderstorms will be capable of producing strong and damaging winds, frequent lightning, and very heavy flooding rains.
Additionally, an increase in storm relative helicity and low level shear suggests the potential may exist for downbursts and isolated tornadoes. If individual supercells can form, this threat could be somewhat greater. Storms are expected to develop over Eastern Pennsylvania this afternoon and shift eastward through NJ, NYC, SE NY and CT. With strengthening wind fields, just above the surface, any storm could produce the aforementioned damaging winds and severe-weather impacts.
The Storm Prediction Center has placed a large majority of our area in a Slight Risk for severe thunderstorms, and additionally has issued a 30% risk for damaging winds — a more enhanced percentage of Slight Risk which attempts to pinpoint an area of more concentrated severe weather potential.
Stay tuned throughout the afternoon and evening for further updates. We encourage you to visit our twitter account for up-to-the minute information and information regarding watches and warnings.